RECLASSIFICATIONS OUT OF ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) - Effects to Net Income of Amounts Reclassified Out of OCI (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net interest income	$ 1,026	$ 923	$ 2,031	$ 1,827
Provision for credit losses	70	90	166	181
Noninterest income	370	355	749	685
Noninterest expense	864	827	1,718	1,638
Income before income tax expense	462	361	896	693
Income tax expense	144	118	258	227
NET INCOME	318	243	638	466
Amount Reclassified from AOCI
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net interest income	7	13	17	27
Noninterest income	(1)	(3)	2	5
Noninterest expense	4	4	9	8
Income tax expense	0	2	3	9
NET INCOME	$ 2	$ 4	$ 7	$ 15